Federal agents yesterday made three visits to the Rhode Island home of the parents of Katherine Russell, 24, an all-American-girl-turned-terrorist’s-bride.

During the first encounter, the agents were in the home for about 10 minutes.

A couple of hours later, The Post observed the same agents — two men and a woman — briefly speaking with Russell’s mom, Judith, through the door. Russell, who has a 3-year-old daughter, Zahara, with Tsarnaev, 26, is believed to have been inside.

One of the male agents was carrying a manila envelope, books and papers and walked away again with them after the brief chat with the mom.

In their final visit last night, the agents spent two hours in the house before leaving, followed by the family’s lawyer, Amato DeLuca.

“We just did some talking. We’re doing our best to try to deal with a very difficult situation. The family is going through a lot,” DeLuca said.

He refused to say whether the agents were with the FBI, ATF or ICE, confirming only that they were with the feds.

“Other than a brief interview with the FBI, there has been nothing more than that,” DeLuca told The Post. “Quite frankly, she was married to that man, so it doesn’t surprise me that they would do something of an investigation.’’

DeLuca later told The Post, “Katherine is innocent, and she has no knowledge of any of this.”

Federal agents had been by the parents’ house on Friday, as well, according to the Daily Mail.

Russell learned her husband was implicated in the terror attack by watching TV, DeLuca said. He did not say whether she identified him for authorities after they posted his image.

Meanwhile, a law-enforcement source told The Post the FBI is scouring video of the marathon and showing Russell’s picture to witnesses to see if she was at or near the finish line when two bombs ripped through the crowd last Monday, killing three people and injuring nearly 200 others.

“We’re looking at [footage] and showing the photo,’’ the source said.

In other developments:

* Tsarnaev’s brother, bombing suspect Dzhokhar Tsarnaev, 19, was awake in the hospital and responding to questions, a source told The Post. The investigators were specifically trying to nail down whether he and Tamerlan were part of a terror cell, ABC reported.

* The brothers were likely planning more attacks with the arsenal they had on them during Friday’s after-midnight shootout, which left Tamerlan mortally wounded, authorities said.

* The suspects’ mother claimed that Tamerlan made a call to her in Russia as he and his brother were being chased by cops, The Wall Street Journal reported. “The police, they have started shooting at us, they are chasing us!” Zubeidat Tsarnaeva told the paper, quoting her son. His last words were, “Mama, I love you,’’ before the phone went dead, she said.

* Although authorities said evidence suggests the two brothers acted alone, some officials insisted that the plot could be part of a bigger terror network.

* A video that Tamerlan appears to have posted on, then deleted from, YouTube featured a jihadist leader who was later killed in a shootout with Russian authorities, CNN said. The video, under the subheading “Terrorists,” featured a militant called Abu Dujana, the alias for a radical named Gadzhimurad Dolgatov.

* ATF agents have recovered enough remnants of one bomb — including a circuit board with wires crudely soldered to it — that they should be able to piece it back together, said Boston Police Commissioner Ed Davis.

The FBI did not respond to questions about Tamerlan’s wife.

On Saturday, Russell was spotted darting in and out of the Cambridge home she had shared with her husband and his brother.

Friends and neighbors said Russell was raised as a Christian but shrouded herself in Muslim garb after becoming involved with Tamerlan and converting to Islam.

They said she dropped out of college and abandoned dreams of joining the Peace Corps.

‘She was just this all-American girl who was brainwashed by her super-religious husband,” one friend told the Daily Mail. “Nobody understands what happened to her.”

In January, her violent husband was kicked out of his Cambridge mosque after an angry outburst against a speaker who compared Martin Luther King Jr. to the Prophet Mohammed, the Los Angeles Times reported.

A neighbor of Russell’s parents told the Mail that the last time she saw Tamerlan was about a year ago and that Russell had “moved back home and was living at home with the baby.”

A team of FBI and CIA interrogators — who handle high-profile terror suspects at Guantanamo Bay — was being flown in to take over the grilling of Tamerlan’s brother, Dzhokhar, sources told The Times of London.

A key question will be whether the brothers had help in their plot, officials said.

Investigators said Monday’s bombing might have roots in Russia, particularly the region where Tamerlan traveled for six months during in 2012, when he was likely “radicalized” by jihadist terrorists, sources said.

Tamerlan had been on the FBI’s radar when the agency investigated him at the request of Russian officials. But they were unable to find evidence he was connected to a terror organization.

Sen. Lindsey Graham (R-SC) told CNN’s “State of the Union,” “Either our laws are insufficient or the FBI failed. But we’re at war with radical Islamists, and we need to up our game.”

Meanwhile, it seems clear the brothers planned on killing again, authorities said. There were three devices that exploded during the shootout — a pressure cooker and two pipe bombs filled with nails — as well as two more pipe bombs found at the scene. Another pipe bomb was found at the brothers’ apartment.

A cop critically wounded in the shootout continued to improve yesterday, after his heart had stopped and he lost nearly all of his blood when a bullet severed three arteries in his right thigh.